The present invention relates in general to a data acquisition technique which is used in association with a conveying system or a hoist system such as one employing a hoist crane. The technique of this invention may be used in association with a programmable conveying or hoisting system. In accordance with the invention there is provided data associated with the product member (work piece) which is being transported in a process such as an electroplating process. The data that is read may be in many different forms in accordance with the invention for different usages. For example, the data may represent a carrier number which would identify the particular parts being processed. Secondly, the data could be representative of decision data to select the particular process station at which a choice in operation may exist. The data may then be read to make this selection. Finally, the data that is read in accordance with this technique may be representative of a critical processing parameter to be used as a form of control at a particular station upon delivery of the product member or pieces to that particular station.
Accordingly, the concepts of this invention have a wide application of usage for the particular data that is read. However, there are a number of restrictions associated with prior art systems which must be overcome. Some of these restrictions or drawbacks are hostile environments, broad positioning tolerances, load sway, physical clearances, and variations of equipment speed in particular with relationship to the interruption and resumption of processing.
One type of prior art arrangement is a parallel-type coded reader which has been used on hoist cranes and which is usually activated at the top of the hoist when the product member is in its transverse attitude. One of the disadvantages of this prior art arrangement is the requirement for a plurality of sensors or switches at a rate of one sensor or switch per bit of data. There is also a space constraint with regard to the mounting of all of these sensors or switches. Furthermore, there is a positioning tolerance with regard to the stopping of the target reliably after each hoist operation. With such systems there is usually a requirement of a settling delay time before reading occurs to insure stable alignment at the time that the data is injected into the controller.
Another prior art arrangement employs parallel sensors that require that signals be transmitted into these sensors. Such sensors also possess the disadvantage of the requirement of a plurality of sensors at a rate of one sensor per bit of information. Additionally, these arrangements have the disadvantage of requiring one group of sensors for each process station or process tank where this data is utilized. In addition to being inflexible relative to placement of the sensors, there is a practical problem which is at least partially environmental of having these sensors at the process tanks. This is an unreliable and hostile environment.
In accordance with another prior art technique product data has been transferred through a plurality of process stations by way of shift register loading. This technique normally includes the inputting of data when the parts are injected into the system, a shifting update as the machine progresses and a reading of data at various points as required by the process stations. Such a technique assumes that the product members are loaded in the same order as they are injected into the system which may not be the situation especially with the requirement of multi-process cycling on the same equipment or where there is frequent interaction with the process sequence as in clearing a fault or semi-reworking unacceptable products before allowing resumption. This technique whether implemented in hardware or in software possesses the same inflexible disadvantages listed previously. With this shift register technique the register must be constructed to the exact data field that is being considered and be shifted each time an index occurs. This thus requires that there be an absolute order of parts relative to the data reading per the process cycle. This design is further complicated when a second process is run on the same system wherein a different relationship between part injection and number of indexes before product data is required exists.
Accordingly, one object of the present invention is to provide an improved data acquisition system and, in particular, one that is usable in association with a conveying system or a hoist system employing a hoist crane.
Another object of the present invention is to provide a data acquisition system that is quite widely usable with a number of different types of control. For example, this system may be used in association with a system shown in U.S. Pat. No. 3,803,561 which discloses a programmable hoist system. The data acquisition system of this invention may be used to identify the parts at a specific station, to make a process variable decision, or to input critical process control information at a specific process station.
A further object of the present invention is to provide an improved data acquisition system as described herein which operates accurately and is not affected by an interruption, or operation of a program not previously intended. In this regard the form of data acquisition of this invention permits a stop and start sequence to occur without loss of data.
Still another object of the present invention is to provide an improved data acquisition system as described herein and which is not affected by such parameters as load sway or variations of equipment speed.
Still another object of the present invention is to provide an improved data acquisition system that is relatively simple in construction having a relatively minimum number of sensors required by employing a serial-type of data sensing system.
Still another object of the present invention is to provide an improve data acquisition system for use with a conveying or hoisting system and which is not materially affected by any hostile environmental conditions or any broad positioning range tolerances.